Fix character spacing in `renderstring!`

[ffreyer]

Running

# render a string into an existing matrix
face = findfont("Dejavu Sans")
pixelsize = 64
x0, y0 = 2, 0
myarray = zeros(UInt8, pixelsize+2, 23pixelsize)
renderstring!(
    myarray, "0123456789qwertzuiopasdfghjklyxcvbnm,.-", face, pixelsize, 
    x0, y0, valign = :vtop
)

scene = Scene(resolution = (size(myarray, 2), size(myarray, 1)))
campixel!(scene)
heatmap!(scene, myarray'[:, end:-1:1], colormap = (:white, :black))
Makie.save("/home/frederic/Desktop/old.png", scene)

currently generates

because the horizontal bearings are applied in the wrong direction. With these changes I get

[codecov[bot]]

Codecov Report

Merging #64 (bf43e8c) into master (4db586e) will increase coverage by 0.33%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #64      +/-   ##
==========================================
+ Coverage   75.25%   75.58%   +0.33%     
==========================================
  Files           6        6              
  Lines         299      299              
==========================================
+ Hits          225      226       +1     
+ Misses         74       73       -1     

Impacted Files	Coverage Δ
src/rendering.jl	93.15% <100.00%> (ø)
src/types.jl	67.96% <0.00%> (+0.97%)	:arrow_up:

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[SimonDanisch]

Interesting, that this creates some artifacts:

[ffreyer]

I've noticed that too, but I don't think that's because of this change. If you look at x or v you can see artifacts in both, but they move a little between the two versions.

[ffreyer]

Saving just v from a 64px render with FileIO: with Makie heatmap:

[SimonDanisch]

Interesting...

[ffreyer]

Oh right - that's because heatmaps are shifted by 0.5. Translating the plot to integer values removes these artifacts.